[srslte-users] Maximum possible MCS with subframes 0 and 5

Felipe Augusto Pereira de Figueiredo zz4fap at gmail.com
Wed Aug 1 20:42:47 UTC 2018


Dear All,

I found on line 896 of the following example that data is never sent
on subframes 0 or 5. Does it mean we can not achieve MCS 28 on those
subframes?

https://github.com/srsLTE/srsLTE/blob/master/lib/examples/pdsch_enodeb.c#L896

Thanks and Kind Regards,

Felipe Augusto

On Mon, Jul 30, 2018 at 11:00 AM, Felipe Augusto Pereira de Figueiredo
<zz4fap at gmail.com> wrote:
> Dear Justin,
>
> Thanks for your reply!
>
> Let's assume perfect channel conditions (then, MCS 28 is theoretically
> possible) and that all the Resource Blocks are allocated to one single user.
>
> My question is, can we use use MCS 28 in subframes 0 and 5? Would it work?
> based on my calculations the code rate is less than 0.93 as mentioned in TS
> 36.213 7.1.7.
>
> What I'm trying to figure out is the maximum possible MCS for subframes 0
> and 5 when channel conditions are perfect and all the RBs are allocated to
> one user.
>
> I hope I could clarify my question a little...
>
> Thanks and Kind Regards,
>
> Felipe Augusto
>
>
>
> On Mon, Jul 30, 2018 at 10:22 AM, Justin Tallon
> <justin.tallon at softwareradiosystems.com> wrote:
>>
>> Hey Felipe,
>>
>> The restriction on the code rate is set by the calculated quality of the
>> channel. The channel quality is estimated and an MCS is chosen that will
>> perform well for the channel state. In certain cases the MCS will also be
>> dropped further if there is limited data needed to be transmitted in that
>> particular transport block.
>>
>> Im not sure if I am answering your question properly? Perhaps you could
>> provide more detail about what you are trying to figure out?
>>
>> Thanks,
>> Justin.
>>
>>
>> ____
>> Justin Tallon Ph.D.
>>
>> Software Radio Systems (SRS)
>> http://www.softwareradiosystems.com
>>
>> +353-86-067-0753 | justin.tallon at softwareradiosystems.com
>>
>> On Sat, Jul 28, 2018 at 10:53 AM, Felipe Augusto Pereira de Figueiredo
>> <zz4fap at gmail.com> wrote:
>>>
>>> Dear All,
>>>
>>> I did some calculations, for example, in subframe 5, there are 684 REs
>>> available for data transmission. Therefore, for MCS values using 64QAM
>>> modulation there are 4968 bits in total available for data
>>> transmission. Considering all the bits added in the DLSCH coding
>>> (CRCA, CRCB, turbo coding) I've found the following code rates for
>>> MCSs 24, 25 and 26.
>>>
>>> MCS 24 code rate of 0.795
>>> MCS 25 code rate of 0.857
>>> MCS 26 code rate of 0.888
>>>
>>> I'm trying to understand if there is any restriction when the code
>>> rate is higher than 0.7 so that we have CRC error when decoding.
>>>
>>> Could you please, shed some light on this matter?
>>>
>>> Many thanks and Kind Regards,
>>>
>>> Felipe Augusto
>>>
>>> On Thu, Jul 26, 2018 at 7:54 PM, Felipe Augusto Pereira de Figueiredo
>>> <zz4fap at gmail.com> wrote:
>>> > Dear All,
>>> >
>>> > I'd like to know what is the maximum possible MCS for subframes 0 and
>>> > 5.
>>> > In my tests, for example for a BW of 1.4 MHz and subframe 5, after MCS
>>> > 23/24 I start having CRC errors.
>>> >
>>> > I know that subframe 0 carries PSS/SSS and BCH and that subframe 5
>>> > carries PSS/SSS but I would like to know from you what is the maximum
>>> > possible MCS.
>>> >
>>> > Thanks and Kind Regards,
>>> >
>>> > Felipe Augusto
>>> _______________________________________________
>>> srslte-users mailing list
>>> srslte-users at lists.softwareradiosystems.com
>>> http://www.softwareradiosystems.com/mailman/listinfo/srslte-users
>>
>>
>


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